Gradated target for X-ray tubes

Abstract

An X-ray tube including a tubular envelope having therein an X-ray target comprised of a support body made of a first material and provided with a composite surface layer comprising a controlled gradient of a second material disposed in the first material, one of the materials being an X-ray emissive material and the other of the materials being a heat absorbent material, and an electron emitting cathode disposed to beam electrons onto a focal spot area of the composite surface layer.

What is claimed is: 
     
       1. An X-ray target including: a support body having a surface overlying a composite layer comprising a first material and a controlled gradient of a second material disposed therein, one of the materials being a heat absorbent material comprised of one or more elemental components having respective atomic numbers no greater than thirty and the other of the materials being an X-ray emissive material comprised of one or more elemental components having respective atomic numbers greater than the atomic numbers of the elemental components of said one of the materials.   
     
     
       2. An X-ray target as set forth in claim 1 wherein the first material is a heat absorbent material comprising one or more elemental components having respective atomic numbers no greater than thirty; and the second material is an X-ray emissive material comprising one or more elemental components having respective atomic numbers greater than the atomic numbers of the elemental components of the first material. 
     
     
       3. An X-ray target as set forth in claim 1 wherein the first material is an X-ray emissive material comprising one or more elemental components having respective atomic numbers greater than thirty; and the second material is a heat absorbent material comprising one or more elemental components having respective atomic numbers less than the atomic numbers of the elemental components of the first material. 
     
     
       4. An X-ray target as set forth in claim 1 wherein the composite layer has a thickness between two and sixty micrometers as measured from the surface. 
     
     
       5. An X-ray target as set forth in claim 2 wherein the composite layer has a thickness between about two and twenty micrometers as measured from the surface. 
     
     
       6. An X-ray target as set forth in claim 1 wherein the second material has a maximum concentration adjacent the surface and a progressively decreasing concentration as a function of depth from the surface. 
     
     
       7. An X-ray target as set forth in claim 6 wherein the concentration of the second material is approximately one hundred percent at the surface and decreases progressively to a desired concentration at a predetermined depth from the surface. 
     
     
       8. An X-ray target as set forth in claim 1 wherein the support body is made of the first material. 
     
     
       9. An X-ray tube including: a tubular envelope;   an X-ray target rotatably mounted in the envelope and having an annular focal track surface overlying a composite layer comprising a first material and a controlled gradient of a second material disposed therein, one of the materials being a heat absorbent material comprised of one or more elemental components having respective atomic numbers no greater than thirty and the other of the materials being an X-ray emissive material comprised of one or more elemental components having respective atomic numbers greater than the atomic numbers of the elemental components of said one of the materials; and   means for beaming electrons into the composite layer and generating X-rays which pass in a beam out of the tube.   
     
     
       10. An X-ray tube as set forth in claim 9 wherein the first material is a heat absorbent material comprising one or more elemental components having respective atomic numbers no greater than thirty; and the second material is an X-ray emissive material comprising one or more elemental components having respective atomic numbers greater than the atomic numbers of the elemental components of the first material. 
     
     
       11. An X-ray tube as set forth in claim 9 wherein the first material is an X-ray emissive material comprising one or more elemental components having respective atomic numbers greater than thirty; and the second material is a heat absorbent material comprising one or more elemental components having respective atomic numbers less than the atomic numbers of the elemental components of the first material. 
     
     
       12. An X-ray tube as set forth in claim 9 wherein the target is made of the first material; and the second material has a maximum concentration adjacent the focal track surface. 
     
     
       13. An X-ray tube as set forth in claim 12 wherein the concentration of second material is approximately one hundred percent at the focal track surface and decreases progressively as a function of depth measured from the surface. 
     
     
       14. An X-ray tube as set forth in claim 13 wherein the composite layer has a thickness between two and sixty micrometers measured from the focal track surface.